This invention relates to a reversible pivoting vane rotary compressor and in particular to a compressor used in a valve-free oxygen concentrator and analogous applications.
Conventional oxygen concentrators often employ a rotary compressor to pump air through the concentrator and to the patient. Such compressors provide a desirably high rate of air flow and do not generate excessive pressures. The typical rotary compressor features carbon vanes that are slidably mounted in generally radial slots in the compressor""s rotor. The rotor itself is eccentrically mounted in a chamber formed in the housing of the compressor. An electric motor drives the rotor such that centrifugal force urges the carbon vanes outwardly from their slots to engage the wall of the chamber. The vanes form successive compartments that collect air that is introduced into the compressor. As the vanes rotate, the air is moved into a gradually constricted portion of the chamber where it is compressed. This compressed air is then delivered through an exhaust port to the concentrator""s filter.
Recently, I developed a valve-free oxygen concentrator. See U.S. Pat. No. 5,968,236. Therein, a reversible motor is operably connected to a pair of compressors, each of which is communicably connected to a respective nitrogen filter. The motor drives each compressor in a forward direction to pump air through the nitrogen filter. As a result, the filter extracts nitrogen from the air pumped therethrough to produce concentrated oxygen. Alternately, the motor drives the compressor in a reverse direction to evacuate the filter. The extracted nitrogen is exhausted from the filter by the compressor.
Conventional carbon vane rotary compressors exhibit a number of significant problems. As each vane slides back and forth within its respective slot, a considerable amount of heat is generated. Moreover, the friction resulting from such sliding causes the vanes to wear and generates carbon dust, which can foul the compressor. As a result, these types of compressors required frequent maintenance. In particular, the dust must be removed an the vanes replaced at regular intervals. Moreover, due to the constant wear on the vanes, known rotary compressors are very likely to exhibit gaps between the ends or tips of the vanes and the chamber wall. This can result in air leakage, which may significantly impair the operation of the compressor and the oxygen concentrator.
Carbon vane compressors cannot be used at all in the valve-free concentrator described above. The carbon vanes are designed to operate in a single direction only. The vanes are not able to instantly change direction so that the compressor operates in the reverse direction when the motor reverses.
I have developed a pivoting vane compressor, which represents a significant improvement over standard carbon vane compressors. See U.S. Pat. No. 5,188,524. That reference features a pivoting vane rotary compressor wherein pairs of opposing vanes mounted to a rotor define pockets or compartments. As the vanes rotate, the respective compartments are gradually constricted to compress the air being transmitted by the machine. Although this product works quite well, it was not developed for use in conjunction with the reversible, valve-free oxygen concentrator. Specifically, the device of U.S. Pat. No. ""524 was again intended principally for operating in a single direction and was not designed for reversible operation. In a valve-free reversible concentrator, balanced, consistent and uninterrupted compressor operation is critical in order for high levels of concentrated oxygen to be continuously and efficiently produced. The two compressors must perform alternately in an equal, complementary and uninterrupted manner in order to provide the respective nitrogen filters with consistent, properly balanced supplies of air. If this is not achieved, the concentrator may produce varying concentrations of oxygen over time, which is quite undesirable. A specific need exists for an improved reversible compressor specifically intended for use in a reversible, valve-free oxygen concentrator and capable of efficiently producing balanced, consistent and uninterrupted high levels of air flow to the nitrogen filters of the concentrator.
It is therefore an object of this invention to provide an improved pivoting vane rotary compressor that is specifically designed for use in a reversible, valve-free oxygen concentrator.
It is a further object of this invention to provide reversible pivoting vane rotary compressors which generate a consistent, balanced and interrupted air flow to the nitrogen filters of a oxygen concentrator so that a consistent high level of concentrated oxygen is produced over a given time.
It is a further object of this invention to provide a reversible pivoting vane rotary compressor that is capable of reversing direction instantaneously and operating in a balanced uninterrupted manner in both compression and vacuum drawing modes.
It is a further object of this invention to provide a reversible pivoting vane rotary compressor wherein each compressor port alternates as an inlet port and as an exhaust port depending upon the direction of the compressor""s rotation so that an efficient, balanced operation is achieved.
It is a further object of this invention to provide a pair of reversible pivoting vane rotary compressors in an oxygen concentrator, which employ equivalent, complementary internal constructions and port structures so that a consistent, well balanced and uninterrupted compressor and concentrator operation is exhibited.
This invention results from a realization that a significantly improved and highly efficient valve-free concentrator may be achieved by employing reversible compressors that utilize identically oriented pairs of alternating intake and exhaust ports. Pumping efficiency is further enhanced by constructing the vanes and the rotor of each compressor such that each vane is driven into flush interengagement with the circumferential surface of the rotor during each rotation of the rotor through a constricted portion of the compression chamber. Adjoining vanes are positioned in close proximity to one another to minimize the size of the compartments or pockets in which the air is being compressed. This improves pumping efficiency. This invention further realizes that an improved, balanced and selected compressor performance may be achieved by orienting the intake and exhaust ports symmetrically at equal radial angles relative to the most constricted region of the compression chamber or at other selection positions which provide corresponding pumping performance. Providing channels in the wall of the compression chamber adjacent to one or more of the ports further improves compressor performance by enhancing air flow and/or reducing drag.
This invention features a reversible pivoting vane rotary compressor including a housing having a generally cylindrical chamber defined by an inner wall. A rotor is mounted eccentrically within the chamber to define about the rotor a generally crescent shaped compression chamber, which narrows from a main chamber region to a constricted chamber region. The rotor has a circumferential surface. There are a pair of reversible intake and exhaust ports connected communicably with the constricted chamber region, each port for selectively and alternately introducing the air into the constricted chamber region while the other port exhausts air from the constricted region. At least one adjoining pair of curved vanes are pivotably attached the rotor and extend generally opposite arcuate directions from the rotor into the chamber. There are means for rotatably driving the rotor alternately in opposing first and second directions such that both of the adjoining vanes are urged simultaneously against the inner wall of the chamber to define at least one compartment that transmits the air through the chamber between the pair of intake and exhaust ports and through the main chamber region. As a result, air introduced through a selected one of the ports is compressed and discharged through the other port.
In a preferred embodiment, the circumferential surface of the rotor and each vane have substantially conforming curvatures and the rotor is positioned within the chamber such that each vane is driven into substantially flush interengagement with the circumferential surface when the vane is driven by the rotor into the constricted chamber region. At least one pair of vanes may extend outwardly from the rotor in a convergent manner and at least one pair of vanes may extend outwardly from the rotor in a divergent manner. The pair of intake and exhaust ports may be oriented about the chamber at equal and opposite radial angles relative to a narrowest portion of the constricted chamber region. One or more channels may be formed in the wall of the chamber in communication with one or more of the ports. This feature achieves improved air intake and/or reduces air resistance and drag near the exhaust port.
An oxygen concentrator may employ at least one and preferably two of the compressors as set forth above. The concentrator may include first and second nitrogen filters. A first reversible pivoting vane rotor compressor may be communicably and operably connected to a first filter and a second reversible pivoting vane rotary compressor may be communicably and operably connected to the second filter. Motor means may be provided for rotatably driving the rotors of the first and second compressors alternately in opposing first and second directions such that in each compressor, both of the adjoining vanes are urged simultaneously against the inner wall of the chamber to define at least one compartment that transmits air through the chamber between the pair of intake and exhaust ports and through the main chamber region. As a result, air introduced through one of the ports is compressed in the chamber and discharged through the other port. The motor means drives the first compressor in a forward direction to pump air into and through the first filter while simultaneously driving the second compressor in a reverse direction to evacuate the second filter. Alternately, the motor means drives the first compressor in a reverse direction to evacuate the first filter while simultaneously driving the second compressor in a forward direction to pump air into and through the second filter.